In the prior art typically in use in the housing construction and carpet installation industries, wooden "tack strips" with nails or other sharp projections sticking up through them are used to fasten carpet to floors at the periphery edges of the wall. These tack strips have to be nailed or glued to the floor surface, which is time consuming and accordingly relatively expensive.
Additionally, in some instances the concrete surface of the floor becomes so hard that it is very difficult to nail the tack strip to the concrete. When this happens the concrete typically cracks and chips.
With respect to the prior art of the patent literature, perhaps the patent that is most relevant to the invention is the U.S. Pat. No. 4,759,096 patent to Dorris issued Jul. 26, 1988. In the Dorris approach a carpet fastening strip, which can be made of "wood, plastic, metal; flexible ceramic material, or combinations of these" materials, rather than being affixed to the floor, is hopefully held in position by segmented, laterally spaced, face board engaging portions. This face board engaging portions, which are bent under the face board, engage its underside with a series of spaced, inclined protrusions or spikes in the embodiments illustrated.
Thus, the interfacing engagements are at only a relatively few points, constituting a relatively small total area, and the holding forces involved are not directly opposed but rather are at acute angles under a spring biasing force with a force components tending to break the interconnection. Such an engagement, with its very limited, point-to-point type of engagement, is not as reliable as is desired, being susceptible to being pulled out of engagement, or to the loss of the springiness of the material, causing it to fail in its holding power.
In contrast, the embodiments of the invention (three exemplary ones are disclosed) are firmly affixed to the back-side or downwardly extending back edge of either the wall board or the base or face board of the wall, with flat, face-to-face surface engagement or at least continuous or substantially extended engagement along the upper, leading edge of the fastening strip. Indeed the more the strip is pulled, the greater the holding power becomes, while the Dorris approach has very little structural strength to overcome before it would fail.
Other patents which might be of general, background interest are the patents to Sutton (U.S. Pat. No. 3,828,391 issued Aug. 13, 1974) and the patent to Manguso (U.S. Pat. No. 3,997,937 issued Dec. 21, 1976). The latter provides anchoring means comprising a series of clips attached to each tack strip, which allows the strip to be nailed to the wall, avoiding, for example, the problem of trying to nail the wooden tack strips to a concrete floor. The former is directed to a "tackless carpet stripping" molded of plastic which is nailed to the floor.
It is believed that a number of other patents directed to carpet fastening systems and tack strips therefor can be found in Class 16, Subclass 16.